Flash and his friends arrive in Arboria and are greeted by a huge swarm of flying, poisonous squirlons. Dr. Zarkov is bitten by a squirlon as the party swings through the tree forests in an attempt to escape the airborne rodents. Prince Barin, Thun and Vultan are reunited with Flash and his friends and all undergo the unknown dangers of the deep caverns, the river dragons and Ming's metalmen's attack before they finally find the rare antidote that saves Dr. Zarkov from the near-fatal squirlon wound.